Wires are among the most important pieces of an electrician’s work. Without them, current could not flow. Splices must be made correctly and effectively for the sake of efficiency and overall safety, because the point at which you splice the wire is the weakest point of the installation. 

History

Prior to the invention of wire nuts, the most common form of wire connection for branch circuitry was to simply strip the wires of a short length of insulation, twist the wires together and tape the resulting joint. This installation may or may not have included soldering the joint together as well. While this process was functional, it was very time consuming and potentially dangerous for several reasons, including the risk of spilling molten solder. 

Crimp-on wire connectors were another way of joining branch circuitry wires. Short lengths of insulation were stripped from the ends of conductors. Then, they were placed side by side. 

A small metal sleeve was then placed over the resulting joint and, using a specialized tool, compressed together to form a solid connection. This produced a functional joint, but the process required another tool to carry around, and it was a dangerous installation if the metal joint wasn’t properly insulated. It was also irreversible—once the crimp was made, if any wires needed to be added or subtracted, the crimp needed to be cut off and the process repeated.

In the early 1910s, an electrician from Canada named William Marr developed the early version of the modern wire nut. The wires were prepared in much the same way. Once stripped, they were twisted together, and a metal sleeve was slid over the joint. The sleeve was not crimped onto the wires, but was held in place with a small grub screw that could be tightened securely. This resulted in a much more positive joint for the conductors, and it installed much faster and could be removed if necessary. A nonconductive ceramic outer cap was slid over the metal sleeve to complete the installation.

Ideal Electrical’s Wing-Nut wire connector

Feeder conductors also often need to be spliced. This was usually accomplished by installing a split bolt at the splice point. A split bolt looks much like a bolt and nut, but with the center portion of the bolt removed. The conductors were then stripped of their insulation, cleaned and then inserted into the bolt’s cavity and tightened down. 

Once the bolt/nut were tightened, several layers of rubber splicing tape was applied over the entire joint, followed by several layers of vinyl electrical tape. The resulting splice was functional, but it was very time consuming to make and fairly large and cumbersome to take apart—especially if that joint had been in place for any length of time.

It should be noted, however, that while not necessarily efficient, if the above methods are done properly, they are effective and can still be used today. This can be especially true in regions that don’t have access to newer technology. Short-term emergency-­type repairs also may be made using these methods. 

Branch wire connectors

Modern wire nuts differ considerably from the connectors Marr invented in the early 20th century, and there are many manufacturers that produce them. Sycamore, Ill.-based Ideal Electrical’s Wing-Nut is popular. The heavy and fragile ceramic outer covering of early wire connectors has been replaced with a strong, nonconductive plastic cover. 

The spring steel core positively holds the wire joint together and the two “wings” on either side of the connector provide extra torque helpful in twisting the wires together. Wing-Nuts also have a wide range of conductor splice combinations and are color-­coded for ease of identification. 

Ideal even offers a wire connector called the “Greenie” made specifically for use on grounding conductors. In lieu of cutting an additional piece of wire to “pigtail” the grounding conductor to the device, the wire connector has a small hole in the top that the ground conductor passes through. Installation is rather simple—cut one of the grounding conductors longer than the others, twist the conductors together with the wire connector while allowing the longer wire to pass through the hole, and attach that longer wire to the device. This allows for a cleaner installation with fewer wires.

Ideal Electrical’s Greenie grounding wire connector

3M, St. Paul, Minn., produces many components for the electrical industry, including wire connectors. The internal metal spring of 3M’s Performance Plus wire connector has greater expansion than most wire connectors, resulting in a wider range of wire-connecting abilities per piece. This, in turn, allows users to stock or carry fewer wire connectors overall. The smoothness of the wire connector and lower-profile twisting wings make it easy to install with less risk of scuffing other conductors (or tearing up fingers). Rounding out the features is a flexible lower skirt meant to prevent the copper from being exposed and becoming an additional safety hazard.

Push-in wire connectors

Push-in wire connectors have been gaining popularity over the past couple of decades for branch wiring and can now be seen in installations just as often as traditional twist-on wire connectors. 

Wago’s 773-104
Push Wire connector
for junction boxes 

In the early 1970s, Wago Corp., Germantown, Wis., released its push-in wire connectors for the European market, but these connectors didn’t gain much traction in the United States until the early 2000s. This technology relies on pressure from a spring steel clip to hold the wires separately, as opposed to all together in a traditional twist-on wire connector, while still allowing for overall connectivity within the splice. Installation efficiency was greatly improved by not having to twist the wires together—users just insert the stripped end into the connector.

More recently, Wago has produced the 221 series of Lever Lock push-in wire connectors that focuses on ease of use—pull the lever up, insert the conductor and then push the lever back down to lock in the conductor. This reduces the time needed to install, remove or change the conductors within the circuit. They are extremely versatile, with a range of conductors from 24 AWG up to 12 AWG. They also can connect solid, stranded and fine-stranded conductors. The 221 series has three different sizes of connectors: two-, three- and five-conductor.

Wago's 221 series three-conductor compact splicing connector

Feeder wire connectors

Feeder conductors have also benefited from technological changes. Twist-on wire connectors are not available in feeder cable sizes; split bolts were among the only options to splice larger wires. 

NSI Industries, Huntersville, N.C., has developed the IPL series of insulated taps that improve efficiency. Operating in much the same way as traditional multiport wire lugs, they rely on a screw to lock the wire in place once inserted. However, the complete outer surface of the assembly is covered in a nonconductive rubberized coating—including removable access plugs for the hex screws. This outer covering completely eliminates the need to tape the joint, cutting down on installation time and overall size. 

The wire size range also makes them perfect for tapping. Also available are connectors with conductor access on either side, allowing for a much larger range of usability options. They are dual-rated for copper and aluminum conductors and rated to –45ºC, making them a great choice for outdoor use. NSI also produces the IPLW series designed for use in either a direct burial or submersible applications that negate the need for epoxies or heat shrink. 

Additional considerations

When choosing wire connectors for an installation, consider the voltage range for the circuit. Some connectors are rated for 300V, while others are capable of operating at the 600V range. The ampacity of the circuit should also be a part of the selection process, as the range is different from connector to connector. 

While outdoor-rated connectors are available, some are only for indoor use. Proper selection requires a thorough understanding of what the connector is rated for and capable of. 

NSI Industries Polaris IPL Multi-Tap4-Port 750 Black Connector SSE

Cost is another important factor worth considering. While many of the newer products take much less time to install, these products come with a higher price point.

Conclusion

Wire splicing isn’t the same old long and tedious process it was in the past. Advances in design and technology, along with new and better materials, have left us with installations that are quicker, cheaper and much more consistently safe than ever before. By selecting the correct splice for the application and the size and quantity of conductors, we can ensure that the installation will perform as designed and last for years to come.

ideal electrical / wago / nsi industries